Louisiana Shrimp Rice Dressing

Bring water and 1/2 teaspoon salt to a boil over high heat in a 4-quart heavy pot, then stir in rice. Cover pot, then reduce heat to low and cook until liquid is absorbed and rice is tender, about 15 minutes.

Remove pot from heat and let stand, covered, 5 minutes. Fluff rice with a fork, then keep covered.

While rice is cooking, cook onions, celery, and bell pepper in oil and butter in a wide 8-quart heavy pot over moderately low heat, stirring occasionally, until pepper is softened, 10 to 12 minutes.

Add garlic, tomatoes with juice, water, cayenne, and remaining 1 1/2 teaspoons salt and simmer, uncovered, breaking up tomatoes with wooden spatula and stirring frequently to prevent scorching, until very thick, 45 to 50 minutes.

Add shrimp and simmer, stirring frequently, until just cooked through, 2 to 3 minutes. Add scallion greens and rice and stir until combined well, then season with salt if desired.